<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>Title</title>
        <style>
            div{
                width: 100px;
                height: 100px;
                border: 1px solid red;
            }
            #d1{
                /*设置绝对定位*//*参照物为上下左右的角为原点*/
                position:absolute;
                left: 0px;
                top: 0px;
            }
            #big{
                width: 200px;
                height:200px;
                margin: 100px 0 0 100px;
                background-color: pink;
/*                !*绝对定位*!
                position: absolute;*/
            }
            #big>div{
                width: 100px;
                height:100px;
                background-color: yellow;
                margin: 50px 0 0 50px;
                /*绝对定位*/
                position: absolute;

            }
            #big>div>div{
                width: 50px;
                height:50px;
                background-color: blue;
                /*绝对定位*/
                position: absolute;
                top: 0;
                left: 0;

            }
        </style>
    </head>
    <body>
        <div id="big">
            <div>
                <div></div>
            </div>
        </div>

        <div id="d1">div1</div>
        <div>div2</div>
        <div>div3</div>
    </body>
</html>